The objective of this research proposal is to better understand the pharmacology and regulation of neuronal nicotinic receptor subtypes. The specific aims are: (1) to compare the pharmacology of alpha2/beta2, alpha3/beta4 and alpha4/beta2 subtypes of nicotinic cholinergic receptors expressed individually in stably transfected mammalian cells (HEK-293 cells); (2) to compare the effects of acute and chronic nicotinic agonist exposure on the regulation of these three nicotinic receptors in these transfected cells. The involvement of neuronal nicotinic receptors in nicotine dependence is evident. However, the roles of each nicotinic receptor subtype in nicotine dependence are not known. A better understanding of nicotinic receptor subtype pharmacology and regulation will facilitate the elucidation of the mechanisms underlying nicotine dependence. Furthermore, nicotinic agonists are currently being studied as potential therapies for Alzheimer's disease and Tourett's syndrome. The roles that nicotinic receptor subtypes play in these diseases are not known, however. Understanding the pharmacology of individual nicotinic receptor subtypes will aid in the rational design of drugs to treat these and potentially other diseases. The transfected cell lines were generated by Dr. Yingxian Xiao in our lab. RNase protection assays were used to screen for expression of nicotinic receptor mRNA in the transfected cell lines. Receptor binding assays and 86Rb+ efflux measurements will be used to compare the pharmacology and regulation of the three nicotinic receptor subtypes individually expressed in these cells lines.